In this example, the error indicate Epel repository cannot be retrieved.
"Cannot retrieve metalink for repository: epel"
Some sysadmins have decided not to use that repo totally as they do not use that repo. E.g. when updating a package, they use
# yum --disablerepo="epel" update httpd
- Clean yum cache
- update the ca-certificate packages while disabling that repository with error.
Clean yum cache
# yum clean all
Update ca-certificate packages
In my Centos 6.3, it required to updated these related packages.